Clarify syntax of new manager events that reports a status.

We do not longer approve "ThisEventOn" and "ThisEventOff" named events,
they need to be named "ThisEvent" with a status header showing the
current status.
(Approved by Mark)
Old events won't be changed to keep backwards compatibility,
until we have a revision plan for the AMI.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@17199 65c4cc65-6c06-0410-ace0-fbb531ad65f3